An automatic analyzer is used to automate a biochemical inspection, an immunoassay, and the like. The automatic analyzer mixes a reagent prepared for each inspection item with a specimen in a reaction vessel and causes them to react. In the automatic analyzer, a measuring section optically measures turbidity or a change in the tone caused in the solution mixture by the reaction. Analysis data represented by the concentration of each inspection item component included in the specimen, the activity of an enzyme, and the like is thus generated.
The immunoassay is done by measuring a change in turbidity of a solution mixture. The turbidity is caused by an aggregation that occurs due to the reaction between an antibody in a reagent and an antigen in a specimen. The turbidity is also caused by an aggregation that occurs due to the reaction between an antibody immobilized to a latex particle in a reagent and an antigen in a specimen.
A method using a reagent containing magnetic particles is also usable. In this method, an aggregate formed by the reaction between an antibody immobilized to a magnetic particle in a reagent and an antigen in a specimen is attracted by a magnet to the inner surfaces (two opposite surfaces) of a reaction vessel, and a change in turbidity of the solution mixture is then measured. That is, the aggregate is magnetically separated from other substances in the solution mixture (magnetic separation).
However, the magnetically separated aggregates readily remain on the inner surfaces of the reaction vessel as a contaminant. Since the reaction vessel is repetitively cleaned and reused for the next measurement, the residual aggregates adversely affect the next measurement.